Regulation of stored energy is essential to most machinery. Various forms of energy storage are in common usage (e.g. chemical, elastic, pneumatic). The control of power flow from inertial energy storage means has proven to be more difficult than from other forms.
Storage of energy by means of inertial energy advanced during the 1980's and 1990's through development of flywheels made from aerospace materials, rotating in near total vacuum and supported on magnetic bearings. Such devices can have energy densities equal to or greater than lead acid storage batteries.
Electrical power backup systems employing such advanced flywheels with an integral motor/generator have been commercialized. The motor function of the electrical power backup system motor/generator drives the flywheel to optimal storage speed when the normal electrical power source is available. The generator function supplies back-up electricity in the case of power outages drawing power from the flywheel.
The electrical power backup system motor/generator need not operate at a specific speed because alternating current of a specific frequency, if required, is maintained with electrical circuitry during backup power generation. The motor/generator therefore spins at a fixed ratio to instantaneous flywheel speed (not a multiple of the alternating current frequency).
Variable speed machinery that must operate at a specific speed in a specific condition (for example a vehicle) requires a control mechanism to accommodate the speed difference between the machinery and the (inherently variable speed) inertial energy storage device.
The application of a continuously variable transmission (CVT) or infinitely variable transmission (IVT) to variable speed machinery is obvious. Control of the power flow through a CVT to machinery that incorporates an inertial energy storage means has been the subject of previous patents. For example, in U.S. Pat. No. 3,672,244 Mr. Nasvytis describes a “foot pedal . . . connected to said [(infinitely variable)] transmission means to decrease the ratio of the transmission upon depression of the foot pedal and increase the ratio upon release of the foot pedal”. The CVT is controlled directly by operator input and there is no feedback.
In cases where the CVT speed ratio is controlled directly by an operator, as with the Mr. Nasvytis' foot pedal, the CVT control position is the operator's input for speed ratio. The rate of change of the CVT ratio is the acceleration input. For machinery in which the CVT ratio can change more rapidly than the machinery can accelerate, the operator must be skilled at not changing the ratio at a rate greater than the machinery can tolerate. The limitation to acceleration of the machinery will in most cases be slippage or breakage. Using an automobile for an example, the limit to acceleration is slippage of the tires; tires would slip if the speed control were changed too quickly.
In the event that the rate of change of the CVT ratio frequently exceeds the acceleration capability of the machinery, even momentarily, and causes slippage, energy is wasted, which is counter to the original goal of using inertial storage.
Operators of machinery need precise control of acceleration in addition to the ability to set speed. A wide variety of machinery is either powered by a combustion engine, controlled with friction braking, or both. Throttle position determines the force (torque) and therefore acceleration of the machinery. Friction braking controls force and therefore deceleration.
Due to the difficulty in controlling acceleration via rate of controller actuation, the predominance of force application controls or the energy wasted due to slippage, direct CVT control of machinery utilizing a inertial energy storage device has not been widely implemented.
An alternative to CVT control has been to utilize two motor/generators (both similar to the backup electrical power system). One motor/generator operates at the same speed as the inertial energy source, the second at the same speed as the machinery. Energy flow is regulated electrically. This system was employed in a concept vehicle developed by Rosen Motors and described in Time Magazine, Sep. 23, 1996.
The cost of two motor/generator units in the two motor/generator system is a drawback of this system. Additionally, electrical motors and conductors sized to supply peak power will have relatively high electrical resistance losses at low power flows.
The prior art for control of power flow from a inertial energy source includes the utilization of a clutch or clutch systems. The clutches accommodate the speed difference between the machinery and a inertial energy storage device and regulate the power flow to and from machinery from an inertial energy storage system.
Representative of clutch systems is the teaching of Mr. Smitley in U.S. Pat. No. 4,342,371. Two over-running clutches, one for forward rotation and one for reverse rotation, may be selectively engaged to transmit power to a storage flywheel through corresponding forward and reverse rotating magnetic clutches. Some slippage of the magnetic clutches is anticipated.
The drawback of clutch systems, whether frictional or magnetic, is that slippage will dissipate energy that could, in the absence of slippage, be transmitted to the machinery or stored in the flywheel.